1979 Islamic Revolution shatters relations between United States and Iran

The unbelievable thing about the Islamic Revolution in Iran is that the United States never saw it coming. CIA reports in the six months leading up to it had nothing to say about the level of unrest in the country, even going so far as to comment that Iran wasn’t even in a “prerevolutionary state.” Clearly they were wrong about that and better intelligence perhaps could have prevented Ayatollah Khomeini from taking over.
The Shah was given refuge in the United States and that further enflamed the passions and angers of Iranians determined to believe the man leading their country for the past 40 years was little more than a puppet for the US. The revolution was fairly swift and from that point on relations between Iran and the United States have been largely bad if not utterly hostile.